LEC 19: GAS EXCHANGE

Cards (15)

  • Atmospheric air vs Alveolar air
    • Atmospheric air:
    • Higher oxygen concentration
    • Lower carbon dioxide concentration
    • Lower humidity
    • Facilitates oxygen absorption in the bloodstream
    • Essential for efficient gas exchange in the lungs
    • Alveolar air:
    • Lower oxygen concentration
    • Higher carbon dioxide concentration
    • Higher humidity
    • Facilitates CO2 elimination from the body
    • Essential for efficient gas exchange in the lungs
  • Dalton's Law

    • Total pressure exerted by a gas mixture = sum of partial pressure of individual gases
    • Pertinent to the composition of alveolar gas
    • Governs the exchange of gases between alveoli and blood during external respiration
  • Henry's Law

    • Amount of gas dissolved in a liquid is proportional to its partial pressure and solubility
    • Dictates the exchange of gases between alveolar air and blood
    • Regulates the dissolution of gases in blood plasma during internal respiration
  • How oxygen is transported in blood
    • 1.5% dissolved in plasma
    • 98.5% bound to hemoglobin in RBCs
  • Hemoglobin's affinity for oxygen
    • Changes based on temperature, partial pressure of carbon dioxide (PCO2), blood pH, production of bisphosphoglyceric acid (BPG) from glycolysis
  • Oxygen-hemoglobin dissociation curve
    • Demonstrates hemoglobin's affinity for oxygen
    • Relatively flat at high partial pressure of oxygen
    • Low PO2 = hemoglobin releases oxygen to tissue, especially during exercise
    • During vigorous exercise = more oxygen is unloaded to tissues despite high plasma PO2 levels
  • Types of hypoxia
    • Anemic hypoxia
    • Ischemic hypoxia
    • Histotoxic hypoxia
    • Hypoxemic hypoxia
  • Carbon monoxide poisoning
    • Caused by carbon monoxide binding to hemoglobin with greater affinity than oxygen
    • Reduces the blood's oxygen-carrying capacity
  • How carbon dioxide is transported in the blood
    • Dissolved in plasma (7-10%)
    • Bound to hemoglobin (20%)
    • Bicarbonate ions (HCO3-) (majority)
  • Conversion of CO2 to bicarbonate ions
    1. CO2 combines with water and dissociates, producing carbonic acid and bicarbonate ions that can release or absorb H+
    2. Chloride ions move into RBC to maintain charge balance ("chloride shift")
  • PO2
    • Controls perfusion by changing arteriolar diameter
    • Optimizes perfusion and maximizes oxygen uptake into the blood
    • Low PO2 in muscles during exercise, hemoglobin easily releases oxygen to body tissues
    • High plasma partial pressures of oxygen, hemoglobins unloads little oxygen
    • During vigorous exercise, plasma partial pressure of oxygen falls dramatically so much more oxygen can be unloaded to the tissues
  • PCO2
    • Controls ventilation by changing bronchiolar diameter
    • Increases ventilation so there can be more rapid release of CO2
  • Carbonic acid-bicarbonate buffer system of the blood is formed when CO2 combines with water and dissociates, producing carbonic acid and bicarbonate ions that can release or absorb H+
  • Slow, shallow breathing
    Causes an increase in CO2 in blood resulting in a drop in pH
  • Rapid, deep breathing
    Causes a decrease in CO2 in blood, resulting a rise in pH